この研究は、無線周波電磁界（RF; 900 MHz、120 μW/cm2、1日4時間ばく露）の事前ばく露によってγ線（60Co、3 Gy）ばく露に対する適応応答（AR）が生じるか否かを成獣雄ICRマウスで調べた。実験は以下の各群（5匹ずつ）で行った。(a) 非ばく露対照群、(b)γ線単独の急性ばく露群、(c) RFばく露群（ばく露日数1、3、5、7、14日の5群）、(d) 前記RFばく露群と同様のばく露終了の4時間後にそれぞれγ線急性ばく露を行った5群。末梢血白血球DNAのアルカリ感受性塩基の損傷および単鎖切断をアルカリコメットアッセイで検査した結果、RFの事前ばく露期間1日+γ線急性ばく露群のDNA損傷レベルはγ線単独の急性ばく露群と同等であった；RFの事前ばく露期間3、5、7、14日群では損傷レベルがばく露日数に応じて漸減し、γ線単独の急性ばく露群とは有意差があった、などの所見を報告している。
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To evaluate the extent of a primary DNA damage in peripheral blood leukocyte in mice pre-exposed to 900 MHz radiofrequency (120 mW/cm²) for 4 hours/day for different days (as adaptive dose) and then subjected to 3 Gy gamma radiation (as challenge dose).
Adaptive response: It is known that different cell types that were exposed to an extremely small adaptation dose of a genotoxic agent are less susceptible to the induction of genetic damage when given a higher challenge dose of the same or similar genotoxic agent. The induction of an adaptive response was shown to be influenced by several factors (e.g. the dose used for adaptation, the dose rate, the time between the adaptation and challenge doses).
Mice were divided into several groups of 5 mice each: (1) unexposed controls, (2) acute exposure to gamma radiation (3 Gy, 60Co), (3) 900 MHz radiofrequency exposure for 4 hours/day for 1, 3, 5, 7 and 14 days, and (5) the same radiofrequency exposure periods + 3 Gy gamma radiation given at 4 hour after radiofrequency exposure on days 1, 3, 5, 7 and 14.
Mice were divided into several groups of 5 mice each: (1) unexposed controls (2) acute exposure to gamma radiation (3 Gy, 60Co) (3) 900 MHz radiofrequency exposure for 4 hours/day for 1, 3, 5, 7 and 14 days (five groups) (4) the same radiofrequency exposure periods + 3 Gy gamma radiation given at 4 hour after radiofrequency exposure on days 1, 3, 5, 7 and 14 (five groups)
The data showed that the extent of DNA damage in mice which were pre-exposed to radiofrequency for 1 day and then subjected to gamma radiation was not significantly different from those animals exposed to gamma radiation alone. However, mice which were pre-exposed to radiofrequency for 3, 5, 7 and 14 days showed a progressively decreased DNA damage and the data were significantly different from those mice exposed to gamma radiation alone.
Thus, the findings indicate that radiofrequency pre-exposure is capable to induce an adaptive response and that the pre-exposure for more than 4 hours for 1 day is necessary to elicit such an adaptive response.